Energy Retaining Toe Valve

ABSTRACT

A downhole tool comprises a mechanical energy storage component that retains energy supplied by a first pressure increase and transfers such energy to actuate another component of the tool. In one aspect, the tool is a toe valve that is activated for opening ports thereon upon application of a first pressure and actuated to open the ports upon application of a second pressure lower than the first pressure.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Application No. 63/203,522, filed on Jul. 26, 2021, the entire contents of which are incorporated herein by reference.

FIELD OF THE DESCRIPTION

The present description generally relates to downhole tools, in particular tools for performing perforation operations. More particularly, the description relates to downhole tools that are capable of being activated when conducting a casing pressure test.

BACKGROUND

In the field of hydrocarbon production, a wellbore is first drilled into a region containing a hydrocarbon-containing subterranean formation. The wellbore is then lined with casing, generally comprising a plurality of tubular components having an outer diameter that is less than the diameter of the wellbore, whereby an annular space is created between the casing and the wellbore. The casing is then secured in the wellbore with a cementing operation, wherein cement is passed through the casing and flowed into the annular space between the casing and the wellbore.

As is known in the art, prior to initiating production of a well, the cemented casing is pressure tested to ensure its integrity and that no leaks are present. Such pressure testing is often a requirement prescribed by governmental regulatory authorities. In conducting such pressure testing operation, the toe of the casing is sealed, and fluid is pumped into bore of the casing, thereby increasing the pressure therein to a specified value. This pressure is maintained for a specified period of time to conduct the test. If no pressure drop is found during the course of the test, the integrity of the casing is confirmed.

To achieve production of a cased well, fluid communication must be created between the hydrocarbon-containing reservoir and the internal bore of the casing. For this purpose, perforations are formed through the cement thereby forming fluid channels between the reservoir and the bore of the casing. These channels allow hydrocarbons from the reservoir to enter the casing and to ultimately be produced at surface. The perforations may be formed using various known tools and methods.

As known in the art, the perforation step may be performed using a toe valve, which comprises a tool formed as part of the casing. Such toe valves generally have a number of fluid ejection ports, usually circumferentially arranged, that are directed radially outwards towards the cement. Generally, the ejection ports are covered with burst plugs or discs or the like, which are designed to remain closed until a pre-set threshold pressure is reached. In operating toe valves, the bore of the casing is pressurized using a fluid, with the pressure being raised beyond a threshold pressure of the burst plugs. At this point, the ports are opened, and pressurized fluid supplied to the casing is ejected to the surrounding cement. The pressure of the fluid is sufficient to create perforations in the cement.

As will be understood, where a pressure integrity test must be performed on the casing, the testing pressure would necessarily exceed the pressure required to open the ports of the toe valve. Thus, with toe valves as described above, there is the problem that conducting a pressure test would result in premature opening of the ports of the toe valve. To address this problem, toe valves have been proposed that incorporate one or more mechanisms to prevent premature opening of the ports. Examples of such known toe valves include those described in: U.S. Pat. Nos. 9,359,864; 9,835,010; and 10,107,072. Another toe valve is disclosed by Chauffe, S. (Hydraulic Toe Valve Specifically Designed for a Cemented Environment, Am. Assoc. Drilling Eng., AADE-13-FTCE-25, 2013). Each of these known valves comprise an arrangement of moving sleeves and rupture discs that are adapted to be activated in multiple stages and generally involve complicated mechanisms that may be prone to failure.

The present description aims to provide an improvement over the known toe valves, in particular, toe valves that are designed to maintain closure of the perforation ports during the pressure testing phase.

SUMMARY OF THE DESCRIPTION

In one aspect, there is provided a toe valve adapted to be deployed in a casing installed in a wellbore that is (i) adapted to be activated during a casing pressure test; and (ii) adapted to be actuated upon application of a second pressure lower than the casing test pressure, where actuation of the valve opens ports thereon.

In one aspect, there is provided a tool for deployment in a wellbore for performing a perforation step, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, wherein the tool comprises:

-   -   a top sub, adapted to be connected to an uphole tubular         component, and a bottom sub, adapted to be connected to a         downhole tubular component;     -   a tubular housing extending between the top sub and the bottom         sub, the tubular housing having a first end connected to the top         sub and a second end connected to the bottom sub, and a wall         with at least one perforation port for fluid communication         through the wall;     -   a slidable sleeve provided within the tubular housing, the         sliding sleeve being axially moveable with respect to the         housing between a closed position, wherein the sleeve covers the         at least one perforation port, and an open position, wherein the         at least one perforation port is exposed allowing fluid         communication through the wall of the tubular housing;     -   the top sub including a plurality of pistons, wherein each         piston comprises a respective first end and second end;     -   the top sub including a biasing means for applying an axial         force against the first ends of the pistons;     -   at least one first valve adapted to permit pressurized fluid         within the lumen of the tool to impinge on the second ends of         the pistons and energize the biasing means; and,     -   at least one second valve adapted to be actuated by the         energized biasing means, whereby, upon actuation, the second         valve provides a fluid channel between the lumen of the tool and         the slidable sleeve.

In another aspect, there is provided a method of operating a tool deployed in a wellbore, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, the tool comprising:

-   -   a top sub, adapted to be connected to an uphole tubular         component, and a bottom sub, adapted to be connected to a         downhole tubular component;     -   a tubular housing extending between the top sub and the bottom         sub, the tubular housing having a wall with at least one port         for fluid communication through the wall;     -   the housing including a slidable sleeve, wherein the sleeve is         axially moveable between a closed position covering the at least         one port, and an open position, wherein the at least one port is         exposed allowing fluid communication through the wall of the         tubular housing;     -   the top sub including a biasing means;     -   the method comprising:     -   pressurizing the lumen of the tool with a fluid under a first         pressure and actuating a first valve to permit the fluid to         energize the biasing means;     -   reducing the pressure within the lumen of the tool and actuating         a second valve to permit fluid within the lumen to impinge on         the sliding sleeve;     -   pressurizing the lumen of the tool with a fluid under a second         pressure to axially shift the sliding sleeve from the closed         position to the open position; and,     -   pressurizing the lumen of the tool with a pressurized fluid to         force the pressurized fluid through the at least one port         provided on the housing.

BRIEF DESCRIPTION OF THE FIGURES

The features of certain embodiments will become more apparent in the following detailed description in which reference is made to the appended figures wherein:

FIG. 1 is a side view of a toe valve according to an aspect of the description.

FIG. 2 is a side view of the top sub shown in FIG. 1 with the valve body housing shown in phantom.

FIG. 3 is a side view of the toe valve of FIG. 1 with the valve body housing removed.

FIG. 4 is a side view of the toe valve of FIG. 3 with the piston housing and spool valve housing removed.

FIG. 5 is a side cross-sectional view of the toe valve of FIG. 1 , in an initial, run-in state.

FIG. 6 is an enlarged partial view of the toe valve of FIG. 4 .

FIG. 7 is an enlarged partial view of the toe valve of FIG. 3 .

FIG. 8 is an enlarged side cross-sectional view of the toe valve of FIG. 1 , in an initial state.

FIG. 9 is an enlarged side cross-sectional view of the toe valve of FIG. 1 in its second state, upon application of casing test pressure.

FIG. 10 is an enlarged side cross-sectional view of the toe valve of FIG. 1 in its third state, after shifting of the spool valve.

FIG. 11 is an enlarged side cross-sectional view of the toe valve of FIG. 1 in its final, actuated state.

FIG. 12 is an enlarged side view of the toe valve of FIG. 1 , without the body housing, in its first state.

FIG. 13 is an enlarged side view of the toe valve of FIG. 1 , without the body housing, in its second state.

FIG. 14 is an enlarged side view of the toe valve of FIG. 1 , without the body housing, in its third state.

FIG. 15 is an enlarged side view of the toe valve of FIG. 1 , without the body housing, in its final, actuated state.

FIG. 16 is a partial side cross-sectional view of the toe valve of FIG. 1 in its initial state.

FIG. 17 is a partial side cross-sectional view of the toe valve of FIG. 1 in its second, pressurized state.

FIG. 18 is a partial side cross-sectional view of the toe valve of FIG. 1 in its third, depressurized state.

FIG. 19 is a graph illustrating the operation of the toe valve according to an aspect of the description.

FIG. 20 is a side perspective view of a piston housing as shown in the figures.

FIG. 21 is a cross-sectional view of the piston housing of FIG. 20 .

FIG. 22 is a side perspective view of a piston pin of the toe valve.

FIG. 23 is a side perspective view of a spool valve housing shown in the figures.

DETAILED DESCRIPTION

As used herein, the term “sub” will be understood to mean a tubing string component, such as a tubular member, a coupling, a tool etc. as known in the art. As also known, a sub has a generally cylindrical structure and is adapted to be connected to adjacent tubular members, or other subs, to form the tubing string. As with typical tubular members, a sub may have a female or “box” end and a male or “pin” end. The box end includes an internal threaded portion that is adapted to receive and threadingly engage an external thread provided on a pin end of an adjacent component (e.g., a tubular member, a sub, or a tool etc.). In this way, all components of the tubular string are connected together in an end-to-end manner.

The term “tool” as used herein will be understood to refer commonly known tubing string components that are used for performing various tasks. Examples of tools include valves, such as sliding sleeve valves, packers, and the like. Cementing tools are also known in the art, and these include plugs, shoes, collars etc.

The term “port” will be understood to mean an opening, aperture, or the like, that is provided to allow the flow of fluid therethrough. As used herein, a port comprises an opening provided on the wall of a tubular body for forming a fluid channel into the lumen of the body.

The terms “comprise”, “comprises”, “comprised” or “comprising” may be used in the present description. As used herein (including the specification and/or the claims), these terms are to be interpreted as open-ended terms and as specifying the presence of the stated features, integers, steps, or components, but not as precluding the presence of one or more other feature, integer, step, component, or a group thereof as would be apparent to persons having ordinary skill in the relevant art. Thus, the term “comprising” as used in this specification means “consisting at least in part of”. When interpreting statements in this specification that include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

The phrase “consisting essentially of” or “consists essentially of” will be understood as generally closed terms, with the exception of allowing inclusion of additional items, materials, components, steps, or elements, that do not materially affect the basic and novel characteristics or function of the item(s) used in connection therewith. For example, trace elements present in a composition, but not affecting the composition's nature or characteristics would be permissible if present under the “consisting essentially of” language, even though not expressly recited in a list of items following such terminology. When using an open-ended term, such as “comprising” or “including”, it will be understood that direct support should be afforded also to “consisting essentially of” language as well as “consisting of” language as if stated explicitly and vice versa. In essence, use of one of these terms in the specification provides support for all of the others.

The term “and/or” can mean “and” or “or”.

Unless stated otherwise herein, the articles “a” and “the”, when used to identify an element, are not intended to constitute a limitation of just one and will, instead, be understood to mean “at least one” or “one or more”.

The terms “top”, “bottom”, “up”, or “down” may be used herein. It will be understood that these terms will be used purely for facilitating the description and, unless stated otherwise, are not intended in any way to limit the description to any spatial or positional orientation. In one example, the terms “top” or “uphole” may be used herein to refer to a direction along the tubing string or component towards the surface. Similarly, the terms “bottom” or “downhole” may be used herein to refer to a direction along the tubing string or component towards the bottom of the well, i.e., away from the surface. As would be known to persons skilled in the art, the “toe” of a well is the portion furthest away from the top of the well.

FIG. 1 illustrates a side view of a toe valve according to an aspect of the description. As shown, the toe valve 10 comprises a tubular valve body housing, or simply housing, 12 provided between a top sub 14 and a bottom sub 16. As known in the art, and as illustrated in further figures accompanied herewith, the housing 12 is connected to the top sub 14 and bottom sub 16 by means of box and pin connections as known in the art. In one aspect, as illustrated in the accompanying figures, the housing 12 is provided with opposed box ends, which are adapted to engage the respective pin ends of the top and bottom subs, 14 and 16. In other aspects, the opposite ends of the valve may have different engaging means. The housing 12 is secured to the respective subs 14 and 16 by means of lock screws 18 and 20. As will be understood, the toe valve 10 is adapted to be formed as part of the casing that is run into to the well (not shown) prior to the cementing operation.

The housing 12 is provided with at least one, and preferably a plurality of ports 22 at a predetermined distance along the length thereof. The ports 22 are generally circumferentially spaced over the housing 12, as shown in FIG. 1 . In the initial state, each port 22 is closed with a barrier plug 24, thereby preventing fluid transfer through the port 22. In particular, and as will be understood from the present description, the barrier plugs 24 serve to prevent cement slurry from entering or otherwise passing through the ports 22 as the toe valve 10 during the cementing operation.

FIG. 2 illustrates the top sub 14 and bottom sub 16 as provided on the toe plug 10. The housing 12 is shown in phantom and all other components of the toe valve are omitted for clarity. As can be seen, the top sub 14 includes a first end 26 that extends into the housing 12. Similarly, the bottom sub 16 also includes first end 28 that extends into the housing 12 and towards the first end 26 of the top sub 14. As also illustrated in FIG. 2 , the first ends 26 and 28 of the subs 14 and 16 do not contact each other, thereby resulting in a gap formed therebetween. As also seen in FIG. 2 , the ports 22 are aligned so as to be positioned over such gap, and preferably proximal to the first end 28 of the bottom sub 16, as will be appreciated from the description herein.

FIG. 3 illustrates the toe valve 10 in an initial, run-in state, with the housing removed to show certain components of the valve. As shown, the toe valve 10 incudes a mechanical biasing element 30 that is coaxially provided over the first end 26 of the top sub 14. The biasing element 30 may comprise a spring, such as a wave spring, a labyrinth spring, or any other such device that serves to provide an axial expansive force after being axially compressed. The purpose of the biasing element 30 is discussed further in the present description. As also shown in FIG. 3 , adjacent the biasing element 30, and opposite to the top sub 14, there is provided a piston housing 32, followed by a spool valve housing 34. Both the piston housing 32 and the spool valve housing 34 comprise generally annular shaped bodies that are adapted to be provided coaxially over the first end 26 of the top sub 14 and, in one aspect, to be secured thereto by means of cooperating threads as illustrated in the accompanying figures, such as, for example, FIGS. 5 and 6 .

FIG. 4 illustrates the toe valve 10 of FIG. 3 with the piston housing 32 and spool valve housing 34 shown in phantom for the purposes of facilitating illustration. FIG. 6 is an enlarged partial view of the toe valve shown in FIG. 4 . As shown in FIG. 6 , and as discussed above, the piston housing 32 and spool valve housing 34 are provided over the first end 26 of the top sub 14 and are provided with cooperative threading that is complementary to threading provided on the first end 26. In this way, the piston housing 32 and spool valve housing 34 are secured to the first end 26 of the top sub 14 and, as a consequence, axial movement of these components with respect to other components of the valve 10 is prevented.

As illustrated further in FIGS. 20 and 21 , the piston housing 32 comprises a generally annular-shaped body and includes a plurality of barrels 90 extending through the body, where the openings extend parallel to the longitudinal axis thereof. The barrels are preferably spaced equidistantly over the circumference of the body, with each barrel including a first opening 91, facing the uphole direction, and an opposite second opening 92, facing the downhole direction. Returning to FIGS. 3-6 , for example, each of the barrels 90 is provided with a piston pin 36 that is adapted to reciprocally advance within the barrel 90 and, more particularly, through the first opening 91. As will be explained below, the second opening 92 is adapted to receive pressurized fluid, which acts upon the piston pins 36, causing such pins to exert or transfer an axially compressive force onto the biasing element 30. The piston pins 36 preferably include at least one circumferential seal, such as shown at 37 in FIGS. 6 and 16-18 to form a seal with the interior of the respective barrels 90. As illustrated, the seals 37 are preferably provided at a downhole end of the piston pins 36. As discussed further below, this arrangement is preferred in view of the reciprocal movement of the piston pins 36 within the barrels 90. FIGS. 20 and 21 further illustrate one or more blind apertures 132 that may optionally be provided on the outer circumference of the piston housing 32 to aid in torquing the piston housing 32 on to the top sub 14. As would be known in the art, the apertures 132 are adapted to receive a tool to aid in tightening the piston housing 32 onto the top sub 14.

FIG. 22 illustrates a piston pin 36 in isolation. As shown, each of the piston pins 36 generally comprises a solid cylindrical body that functions as a piston within a respective barrel 90. The piston pin 36 includes a first end 124 that faces the uphole direction when the toe valve 10 is installed, and second end 125. The first end 124 is provided with a larger outer diameter, which, as shown in FIGS. 16-18 , prevents the piston pin 36 from extending completely into the barrel 90. Proximal to the second end 125, the piston pin 36 is provided with at least one groove 127, which are adapted to receive seals 37 discussed above. The present figures illustrate the presence of groove 127 on the piston pins and, accordingly, two seals 37. It will be understood that this is one aspect of the description, and any number of seals may be accommodated for. As noted above, the seals 37 are provided to sealingly engage the wall of the barrel 90 when the pin 36 is inserted so as to prevent pressurized fluid from flowing through the barrel 90.

As mentioned above, FIGS. 4 to 6 also illustrate the spool valve housing 34 that, as with the piston housing 32, is preferably coaxially provided over and threadingly secured to the first end 26 of the top sub 14. As more clearly seen in FIGS. 5 and 6 , the spool valve housing 34 is provided with at least one spool valve 38 and at least one check valve 40. As will be discussed further below, the spool valve 38 allows the transmission of pressure there-through in a downhole direction, that is, a direction from the top end of the toe valve 10 to the bottom end thereof. The check valve 40, on the other hand, allows the transmission of pressure therethrough in an uphole direction, that is, a direction from the bottom to the top end of the toe valve 10. It will be understood that the phrase “transmission of pressure” refers to the transmission of a pressurized fluid from a high pressure zone to a zone of lower pressure.

The piston housing 32 and spool valve housing 34 are sealed against the housing 12. In one preferred aspect, the piston housing 32 and spool valve housing 34 are provided with at least two circumferential grooves generally at the opposite ends thereof. FIGS. 20 and 21 illustrate such grooves at 93 and 94 with respect to the piston housing 32. Similarly, FIG. 23 illustrates such grooves at 95, 96, and 97 with respect to the spool valve housing 34. The grooves are adapted to receive a sealing means or element, which may comprise an O-ring or the like. In a preferred aspect, the grooves are further adapted to receive a respective backup ring, such as shown at 42, which are generally U-shaped rings that open in the same direction as the grooves. The rings 42 are adapted to receive and retain a resilient sealing member, such as an O-ring as shown at 43 a, 43 b, 45 a, 45 b, and 49 in the accompanying figures. As illustrated, seals 43 a and 43 b are provided generally on opposite ends of the piston housing 32. The spool valve housing 34 is provided with a pair of opposed seals, shown at 45 a and 45 b, proximal to the downhole facing end of the housing 34, and at least one seal, shown at 49, located proximal to the uphole facing end of the housing 34. FIG. 6 illustrates the backup rings 42 and associated seals in phantom for ease of illustration. It will be understood that the presence of the backup rings is preferred and that the seals, or O-rings, may be provided directly into the grooves on one or both of the piston housing 32 and spool valve housing 34.

FIGS. 4 and 6 also illustrate a shear pin 44 provided on the spool valve 38, which retains the spool valve in position with respect to the spool valve housing 34 until the spool valve is actuated. As more clearly seen in FIG. 6 , at least one port 47 is provided on the spool valve housing 34, with each such ports 47 being provided with a burst plug, or burst disc 46 (for the purpose of the present description, the term “burst disc” and “burst plug” will be understood as representing the same feature). As further illustrated, the burst disc 46 may optionally be provided with a filter insert 48 for preventing debris from collecting. These features are further illustrated in FIG. 7 , which is an enlarged view of a portion of the toe valve shown in FIG. 3 , showing the spool valve housing 34 without the valve body housing 12.

FIG. 23 illustrates the spool valve housing 34 in isolation. As discussed further below, the spool valve housing 34 comprises a generally annular shaped body having a first port 47 on its outer surface, which extends radially through the body and which, in the initial state, is sealed with a burst disc 46. The side of the spool valve housing 34 also includes a second port 116 and third port 117, which do not extend through the body of the spool valve housing 34. Instead, the second and third ports 116 and 117 are in fluid communication with respective channels that extend axially through the spool valve housing 34 in a direction towards the uphole end of the housing 34, when comprising a component of the toe valve. Second port 116 is in fluid communication with a check valve port 118 provided on the uphole facing end of the spool valve housing 34. The check valve 40 (discussed above) is secured to the check valve port 118 and allows flow of fluid from the second port 116 and through the check valve port 118 but not in reverse. A spool valve port 120 is provided on the uphole facing end of the spool valve housing 34 and is in fluid communication with the third port 117. The spool valve 38 (discussed above) is provided within the channel extending between the third port 117 and the spool valve port 120. The spool valve 38 permits fluid to flow from the spool valve port 120 to the third port 117, but not in reverse. As known in the art, a spool valve comprises an axially moving cylinder which opens a fluid flow channel. For this purpose, the third port 120 is preferably provided with a groove 122 to accommodate a portion of the spool valve 38 when such valve is actuated. In a preferred aspect, the spool valve housing 34 includes a circumferentially extending groove 73, comprising a region of reduced outer diameter, which is provided between grooves 96 and 97. Grooves 96 and 97 are adapted to receive seals 45 a and 45 b, respectively, either alone or in combination with retaining rings are discussed above. When combined with the body housing 12, the groove 73 forms annular space 74 bounded by the body housing 12, the groove 73 of the spool valve housing 34, and the opposed seals 45 a and 45 b. As illustrated in FIG. 23 , the ports 47, 116, and 117 are preferably provided in the region of the groove 73, whereby each port is in fluid communication with the annular space 74 that is formed. As discussed above with respect to the piston housing, the spool valve housing 34 may also optionally be provided with one or more blind apertures 134 on the outer surface thereof, which are adapted to receive a tool to aid in securing the spool valve housing 34 onto the top sub 14.

FIGS. 3 to 7 further illustrate a nose coupling 50 that is threadingly coupled to the spool valve housing 34. Optionally, at least one further burst disc 52 may be provided in respective ports on the nose coupling 50. The optional burst disc 52 serves as a backup, or redundancy, and is designed with a burst threshold pressure that is higher than that used for the casing test. The redundant burst disc 52 is provided for situations where the normal operation of the toe valve fails. In such case, the pressure applied to the casing can be increased to actuate the redundant burst disc 52 and thereby activate the toe valve without the need to run in further activating tools.

As illustrated in FIGS. 3 to 7 , the toe valve 10 further includes a sliding sleeve, or “sleeve piston”, or simply “sleeve”, 54 provided coaxially under the valve body housing 12 and is adapted to be axially moved with respect to the housing 12. As shown, in, for example, FIGS. 8 and 9 , the sleeve 54 is initially axially positioned to be aligned with the ports 22 of the valve body housing 12 and thereby cover the ports. As known in the art, sliding sleeves, such as sleeve 54, comprise a generally cylindrical body that is shifted between a “closed” position, where the sleeve covers ports, and an “open” position, where it no longer closes ports. The sliding sleeve 54 is sealed at positions proximal to its opposite ends against the inner surface of the valve body housing 12. In particular, the seals are provided so as to form a sealed annular space bounded by the sleeve 54 and the housing 12 at a region including the ports. Such sealing is accomplished by any known methods. In a preferred aspect, the sealing is achieved by providing circumferential seals, such as O-rings, between the sleeve 54 and the housing 12. For this purpose, the inner surface of the valve body housing 12 is preferably provided with grooves on the inner surface thereof that are adapted to receive respective seals and wherein the grooves are provided proximal to the ends of the sleeve 54 when the sleeve is in its initial position. More preferably, the grooves provided on the valve body housing 12 may be adapted to receive respective backup rings 56, such as shown in the figures, where each backup ring is adapted to receive a seal, such as an O-ring. Such seals are shown, for instance, at 68 and 70 in FIG. 7 . As would be understood, the seals 68 and 70 are adapted to form a pressure seal against the inner diameter of the housing 12, thereby preventing any pressure within the toe valve from being exposed to the ports 22.

As noted above, the sliding sleeve 54 is slidably provided on the valve 10, with the sleeve initially retained in the position shown in FIGS. 3 to 7 by means of a shear ring 60, as shown in FIG. 5 . Other means for retaining the sleeve 54 in its initial position would be known in the art. As discussed further below, when the valve is activated, that is, when the valve is placed in a state where it is capable of being actuated for the perforation step, the sliding sleeve 54 is moved laterally towards the bottom sub 16 and into annular sleeve receiving space 62.

The operation of the subject toe valve will now be described in reference to the figures contained herein.

As described below, the toe valve 10 described herein generally has four states, each of which is briefly summarized below and explained in further detail later in this description. The valve is in its initial state when it, along with the casing, is run into the wellbore. In this state, the ports 22, through which a perforating fluid is ultimately passed, are closed and sealed by the sliding sleeve 54. Once the casing, including the valve 10, is located in the wellbore, the casing is cemented in place, using procedures known in the art. In short, and as described above, cement is provided through the casing and allowed to flow exit the casing and return to surface through the annular space between the casing and the wellbore. During this cementing step, the valve is retained in its initial state.

Once the cementing operation is completed, a pressure test is conducted on the cemented casing as known in the art. As noted, for a pressure test, the interior of the casing, which includes the toe valve 10, is pressurized after sealing the toe of the casing, and the pressure monitored for changes over a given time. Upon pressurizing the casing, the toe valve 10 is actuated to its pressure test state. In this state, the pressure used for the casing integrity test is translated to a force for compressing, or energizing, the spring or biasing element 30 (as discussed further below). The valve 10 is retained in this state while the casing test is conducted. After the test, and as the pressure in the casing is reduced, the biasing element 30 acts on the piston housing 32 to shift or actuate the spool valve 38. The toe valve 10 then enters its third, or activated state. Finally, when the perforation operation is to commence, pressure in the casing, and thus the lumen of the valve 10, is once again increased using a pressurized fluid to cause shifting of the sliding sleeve 54, thereby placing the valve in its final or actuated state. In this state, the ports 22 of the valve 10 are opened and the pressurized fluid is ejected out of the ports and against the adjacent cement. The fluid is thus used to perforate the cement as known in the art. It will be understood that the applied pressure would also dislodge the barrier plugs 24 covering the ports 22.

FIGS. 8 to 11 illustrate enlarged cross sectional views of the valve 10 in its various states. FIGS. 12 to 15 are enlarged side views of the valve 10 in side views in its various states, but without the body housing 12 for ease of illustration. In addition, and solely for ease of reference, the barrier plugs 24 provided in the ports 22 of the housing 12 are shown in FIGS. 12 to 15 .

As noted above, FIGS. 8-10, 12-14, and 16-18 illustrate the sliding sleeve 54 in its initial position, which is maintained by shear ring 60 or other such retaining device. FIGS. 11 and 15 illustrate the toe valve 10 in its final or actuated state, with the sliding sleeve advanced into the sleeve receiving annular space 62. In FIG. 15 , however, the sleeve 54, is not shown, but will be understood as being shifted as discussed above. As noted previously, the plugs 24 are shown in FIG. 15 simply for representing relative positions. It will be understood that the plugs 24 are provided on the ports 22 provided on the body housing 12, which is not shown in FIGS. 12-15 for convenience.

The operation of the toe valve will now be described in more detail with reference to the accompanying figures.

State 1—Initial State of Toe Valve

FIGS. 8, 12, and 16 illustrate the toe valve 10 in its initial state when run in the wellbore and prior to any pressure testing of the casing. As discussed above, when the valve 10 is ultimately used for the perforation phase, the ports 22 provided on the valve 10 allow pressurized fluid conducted through the casing to be ejected from the lumen of the valve and to perforate the cement. Thus, in the initial state of the valve 10, the ports 22 are covered by the sliding sleeve, or sleeve, 54 so that a pressure test of the casing can be conducted. In addition, and as described above, each of the ports 22 may preferably be covered by a barrier plug 24, which is adapted to remain in place and prevent obstruction of the ports 22 until the valve is to be actuated. In one aspect, the barrier plugs 24 serve to prevent material, such as cement during the cementing operation, from entering the ports 22.

As mentioned above, the sleeve 54 is retained in this initial position by a locking means, such as a retaining ring 60 or the like. As will be understood, the retaining ring 60 serves to prevent axial movement of the sleeve within the valve 10.

The sleeve 54 is sealed against the first end 28 of the bottom sub 16 by one or more seals 64, such as O-rings. The sleeve 54 is also sealed against the nose coupling 50 by means of one or more seals, such as O-rings 66. As mentioned above, the sleeve 54 is further sealed against the body housing 12 by means of seals 68 and 70 provided on opposite ends of the region where the ports 22 are located. As will be understood, in this initial state, a sealed annular space is formed, bounded by the region of the body housing 12 having the ports 22, the sleeve 54 and the seals 68 and 70 and seals 64 and 66. In this way, the ports 22 are not exposed to any pressure variations in the lumen of the valve 10 and no fluids are able to pass from the casing through the ports 22.

As also shown in FIGS. 8 and 12 , the biasing element, or spring, 30 is provided between a shoulder 72 on the top sub 14 and the piston housing 32. As will be understood, the shoulder 72 limits axial movement of the biasing element 30 in the uphole direction.

FIG. 16 illustrates the toe valve 10 in its initial state prior to any pressurization. As can be seen, the piston pins 36 are in their initial, retracted positions withing their respective barrels 90. The spool valve 38 can also be seen in its initial state having a spool 78 extending between the first annular space 74 and towards the second annular space 76 and, therefore, the second openings 92 of the barrels 90. An outlet port 80 is provided on the spool 78, which, in the initial state is closed, as shown in FIG. 16 , by a seal formed between the port 80 and the spool valve housing 34. In a preferred aspect, the spool 78 is retained in its initial state by a locking device, such as a shear pin 82, which may, for example, be received within a recess or slot 84 in the spool valve housing 34.

State 2—Pressure Test

FIGS. 9, 13, and 17 illustrate the toe valve 10 in its second state. As mentioned above, this state is entered once the casing pressure test is commenced. When conducting the pressure test, and as is known in the art, the pressure within the casing is increased to a prescribed test pressure and maintained for a prescribed period of time. In the presently described toe valve 10, the burst disc 46, provided on the spool valve housing 34, is selected to rupture once the pressure within the casing reaches the predetermined test pressure. Once the burst disc 46 is ruptured, the port 47 on the spool valve housing 34 is opened and the pressurized fluid used for conducting the pressure test enters into the first generally annular space 74, which, as discussed above, is bounded by the groove 73 of the spool valve housing 34, the body housing 12, and the respective seals 45 a and 45 b provided on the spool valve housing 34. Once in the first annular space 74, the pressurized fluid enters port 116 and passes through check valve 40 provided on the spool valve housing 34 and is allowed to flow out of check valve port 118. As discussed above, the spool valve 38 prevents the pressurized fluid from flowing through port 117. Once the pressurized fluid exits the check valve port 118, it enters a second generally annular space 76, which, as shown in FIGS. 16-18 , is bounded by the seal 43 b of the piston housing 32, the seal 49 of the spool valve housing 34 and the body housing 12. As also shown in FIGS. 16-18 , the second openings 92 of the barrels 90 provided on the piston housing 32 open into the second annular space 76. Consequently, the pressurized fluid entering the second annular space 76 acts upon the second ends 126 of the piston pins 36, thereby forcing the pins 36 to advance axially in the uphole direction within the respective barrels 90. As mentioned above, the seals 37 provided on the piston pins 36 prevent the pressurized fluid from passing through the barrels 90. The advancing piston pins 36 in turn apply an axially compressive force against the biasing element or spring 30 resulting in the biasing element, or spring, 30 being energized.

It should be noted that, in states 1 and 2, both ends of the spool valve 38 are subjected to the same pressure. Therefore, in this pressure balanced state, the spool valve 38 is not actuated. This is shown in more detail in FIG. 17 , which illustrates that, upon increasing the pressure within the casing to the casing testing pressure, the piston pins 36 are axially moved against the biasing element 30 thereby compressing and energizing same. FIG. 17 also illustrates that the spool valve 38 is not shifted during this step as pressure on both ends of the spool is balanced. In other words, the pressure in the barrels 90 (i.e., the pressure in the second annular space 76) and the spool valve port 120 (i.e., the pressure in the first annular space 74) is roughly equal.

As shown in FIGS. 16-18 , for example, the axial advancement of the piston pins 36 in the uphole direction is limited by a stop, such as a circumferentially extending shoulder 128 that is provided on the outer surface of the first end 26 of top sub 14. Such shoulder prevents the piston pins 36 from being ejected from the respective barrels 90 during this step.

As noted above, the check valve 40 only permits transmission of pressurized fluid in the uphole direction. In other words, once the pressurized fluid passes through the check valve 40 and advances, or actuates, the piston pins 36, such pressure is maintained on the piston pins 36, whereby the compressive force on the biasing element 30 is also maintained. In this way, the force exerted on the piston pins 36 by the pressurized fluid is stored in the energized biasing element 30.

State 3—Activation of the Toe Valve

Once the casing pressure test is completed, the pressure within the casing is reduced. This state of the toe valve is illustrated in FIGS. 10, 14, and 18 . Since the lumen of the toe valve 10 is in fluid communication with the first annular space 74 (as a result of the burst disc 46 being ruptured), a reduction in the casing pressure also results in a commensurate reduction in the pressure within the first annular space 74. However, as will be understood, the fluid contained in the second annular space 76 is maintained in a pressurized state as a result of the application of energy stored in the energized biasing means 30, which, in turn, acts on the first ends 124 of the piston pins 36 to force the piston pins 36 in the downhole direction within the respective barrels 90. As noted above, the check valve 40 prevents transfer of the pressurized fluid therethrough. Consequently, a pressure differential is established between the lower pressure in the first annular space 74 and the previous higher pressure in the second annular space 76. This pressure imbalance is imposed on the spool valve 38. In particular, when in this state, the downhole end of the spool 78 is exposed to a lower pressure in the first annular space 74 through third port 117 provided on spool valve housing 34. Simultaneously, the uphole end of the spool 78 is exposed, through spool port valve 120, to the pressurized fluid contained in the second annular space 76. This pressure imbalance thus actuates the spool valve 38, which causes shearing or dislodging of the shear pin 82 from the recess 84 and axial advancement of the spool 78 in the downhole direction.

FIG. 18 illustrates the toe valve once the pressure in the casing is reduced following completion of the pressure test. In this state, the reduction of pressure in the casing, and therefore the lumen of the toe valve 10 reduces the pressure within the first annular space 74, which remains in fluid communication with the lumen of the toe valve 10 following rupture of the rupture disc 46. As shown, this difference in pressure urges the spool 78 in the downhole direction. The spool 78 of the spool valve 38 is now in its second state, wherein, following shearing of the shear pin 82, the spool 78 is shifted in the downhole direction, whereby the outlet port 80 of the spool 78 becomes aligned with a vent port 86 provided on the spool valve housing 34. In this position, fluid communication is established between the lumen of the toe valve, the first annular space 74 and a third annular space 88 that is bounded by the body housing 12, the nose coupling 50, and the sliding sleeve 54. In other words, with the shifting of the spool 78, a fluid communication channel is established between the lumen of the toe valve 10 and the annular space 88 adjacent the sliding sleeve 54. In this state, the toe valve 10 may be described as being activated. In other words, the toe valve 10 is now in a state to be actuated to perform the perforation step, as discussed further below.

It will be understood that the shear pin 82 will be selected according to the anticipated pressure differential established between the annular spaces 74 and 76. Thus, the shear pin 82 serves to retain the spool 78 in its initial state until such time as a predetermined pressure differential is created between the two annular spaces 74 and 76.

As mentioned above, axial advancement, or shifting, of the spool 78 in the downhole directly is limited by the shoulder 130 (as shown in FIGS. 16-18 and 23 ) provided on the spool valve housing 34 and, more particularly, provided within the spool valve port 120. FIG. 18 illustrates the spool 78 in its fully shifted state. In this state, and as mentioned above, the outlet port 80 of the spool 78 is aligned with a vent port 86 provided on the spool valve housing 34. In the result, and as mentioned above, a fluid communication channel is thus established between the lumen of the toe valve 10 and the third annular space 88, thereby placing the toe valve 10 in an activated state in which it is capable of being actuated for a perforation step (discussed below).

State 4—Actuation of the Toe Valve

As will be understood, once the toe valve 10 is in the activated state, i.e., state 3, it is in a state that would allow opening of the ports 22 once the sliding sleeve 54 is laterally shifted in the downhole direction from its initial position as shown in FIGS. 8-10 to its final position shown in FIG. 11 . For shifting the sliding sleeve 54 in this manner, the casing, and thus the toe valve 10, is again pressurized from surface. As will be understood, this is accomplished by providing a pressurized fluid through the casing and into the lumen of the toe valve, with such pressure being chosen to be sufficient to cause shifting of the sleeve. In one aspect, the pressure of the fluid used to shift the sliding sleeve 54 to open the ports 22 may be lower than that used for the pressurization test mentioned above; however, it will be understood that any pressure may be applied as needed.

Once the casing is pressurized, the pressurized fluid enters the first annular space 74 through the port 47 and subsequently to the third annular space 88 through the spool valve 38. In other words, the pressurized fluid applied within the casing enters the first annular space 74 and, thereby, the spool port 120. The fluid then passes through the spool 78, and through the aligned ports 80 and 86, and ultimately into the third annular space 88, which is in fluid communication with the sliding sleeve 54. Upon application of a predetermined pressure, the shear ring 60 retaining the sliding sleeve 54 is sheared and the sliding sleeve 54 is thereby axially advanced in the downhole direction into the sleeve receiving annular space 62. As shown in FIG. 11 once the sliding sleeve 54 is displaced in this manner, the ports 22 are exposed to the lumen of the toe valve 10 and are therefore “opened”. Accordingly, the pressurized fluid supplied into the toe valve 10 will be ejected out of the ports 22 and against the cement lining the wellbore. The receiving annular space 62 may contain a compressible gas capable of allowing the sliding sleeve 54 to extend therein.

As will be understood, the present description provides, in one aspect, a toe valve that can be deployed on casing prior to a cementing operation and retained in place during a casing pressure test without being actuated. Actuation of the toe valve to conduct a perforation operation utilizing such valve, may then be accomplished after the casing pressure test is completed.

FIG. 19 schematically illustrates the performance of the toe valve described herein and comprises a plot of pressure (P) and time and graphically illustrates the various states of the valve mentioned above. In FIG. 19 , the initial state of the toe valve is represented by reference numeral 100. Once the cementing operation is completed, the pressure within the casing is increased, as illustrated at 102. The pressure within the casing, and therefore the toe valve, is increased until the burst disc 46 ruptures, which state is shown at 104. At this point, a slight drop in pressure is experienced by the toe valve as the fluid enters into the first annular space 74, passes through the check valve 40, and acts upon the piston pins 36 and, ultimately, on the biasing element 30. As discussed above, the axial movement of the piston pins 36 compresses, or energizes the biasing element 30, which may be a spring, or, more specifically a wave spring or labyrinth spring. The application of pressure is continued until the prescribed casing test pressure, or PT, is reached, as shown at 106. This pressure is then maintained for the prescribed period of time for conducting the pressure test, as shown at 108. Once the test period is complete, the pressure in the casing is reduced, as shown at 110, resulting in a pressure differential being established between lower pressure in the first annular space 74 and the higher pressure in the second annular space 76, resulting from the expansion force of the energized biasing element 30 acting on the piston pins 36. Once the pressure in the casing is reduced to a predetermined point, as indicated at 112, the pressure differential on opposite ends of the spool valve 38 is sufficient to shear the shear pin 82 retaining the spool 78. As discussed above, at this point, the spool 78 is shifted causing the ports 80 and 86 to be aligned thereby establishing a fluid communication between the casing (i.e., the lumen of the toe valve) and the third annular 88 adjacent the sliding sleeve 54. The pressure may then be reduced to a resting pressure, P₁. As mentioned above, the toe valve is now in its activated state. In order to actuate the valve, to conduct a perforation operation, the casing pressure is increased to a value P₂, as shown at 114, at which point the sliding sleeve 54 is shifted to its open position. In this state, the ports 22 of the toe valve 10 are opened and a perforation procedure may be performed.

It will be appreciated that, while the present description has been provided in relation to a toe valve, the components mentioned above, and the associated method steps, would be applicable to any valve where the energy provided with an increased pressure is mechanically stored or retained and used to actuate a component thereof.

Although the above description includes reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art. Any examples provided herein are included solely for the purpose of illustration and are not intended to be limiting in any way. Any drawings provided herein are solely for the purpose of illustrating various aspects of the description and are not intended to be drawn to scale or to be limiting in any way. The scope of the claims appended hereto should not be limited by the preferred embodiments set forth in the above description but should be given the broadest interpretation consistent with the present specification as a whole. The disclosures of all prior art recited herein are incorporated herein by reference in their entirety. 

We claim:
 1. A tool for deployment in a wellbore for performing a perforation step, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, wherein the tool comprises: a top sub, adapted to be connected to an uphole tubular component, and a bottom sub, adapted to be connected to a downhole tubular component; a tubular housing extending between the top sub and the bottom sub, the tubular housing having a first end connected to the top sub and a second end connected to the bottom sub, and a wall with at least one perforation port for fluid communication through the wall; a slidable sleeve provided within the tubular housing, the sliding sleeve being axially moveable with respect to the housing between a closed position, wherein the sleeve covers the at least one perforation port, and an open position, wherein the at least one perforation port is exposed allowing fluid communication through the wall of the tubular housing; the top sub including a plurality of pistons, wherein each piston comprises a respective first end and second end; the top sub including a biasing means for applying an axial force against the first ends of the pistons; at least one first valve adapted to permit pressurized fluid within the lumen of the tool to impinge on the second ends of the pistons and energize the biasing means; and, at least one second valve adapted to be actuated by the energized biasing means, whereby, upon actuation, the second valve provides a fluid channel between the lumen of the tool and the slidable sleeve.
 2. The tool of claim 1, wherein the sliding sleeve comprises a cylindrical body coaxially provided within the tubular body.
 3. The tool of claim 1 further comprising a means of retaining the sliding sleeve in the closed position.
 4. The tool of claim 1, wherein the sliding sleeve includes a plurality of seals to prevent flow of fluid there-around when in the closed position.
 5. The tool of claim 1, wherein the pistons are circumferentially spaced apart.
 6. The tool of claim 5, wherein the pistons are provided within a piston housing connected to the top sub.
 7. The tool of claim 6, wherein the piston housing comprises a generally cylindrical body having a plurality of barrels for housing the pistons, wherein the second ends of the pistons are contained within respective apertures.
 8. The tool of claim 1, wherein the top sub includes at least one actuation port for transferring pressurized fluid from the lumen of the tool to the second ends of the pistons.
 9. The tool of claim 8, wherein the at least one actuation port is provided with a burst plug.
 10. The tool of claim 1, wherein the at least one first valve is a check valve.
 11. The tool of claim 1, wherein the at least one second valve is a spool valve.
 12. The tool of claim 1, wherein the biasing means comprises a spring.
 13. The tool of claim 12, wherein the spring comprises a wave spring or a labyrinth spring.
 14. A method of operating a tool deployed in a wellbore, the tool comprising a generally tubular structure adapted to be assembled on a tubular string, the tool comprising: a top sub, adapted to be connected to an uphole tubular component, and a bottom sub, adapted to be connected to a downhole tubular component; a tubular housing extending between the top sub and the bottom sub, the tubular housing having a wall with at least one port for fluid communication through the wall; the housing including a slidable sleeve, wherein the sleeve is axially moveable between a closed position covering the at least one port, and an open position, wherein the at least one port is exposed allowing fluid communication through the wall of the tubular housing; the top sub including a biasing means; the method comprising: pressurizing the lumen of the tool with a fluid under a first pressure and actuating a first valve to permit the fluid to energize the biasing means; reducing the pressure within the lumen of the tool and actuating a second valve to permit fluid within the lumen to impinge on the sliding sleeve; pressurizing the lumen of the tool with a fluid under a second pressure to axially shift the sliding sleeve from the closed position to the open position; and, pressurizing the lumen of the tool with a pressurized fluid to force the pressurized fluid through the at least one port provided on the housing.
 15. The method of claim 14, wherein energizing the biasing means comprises compressing a spring.
 16. The method of claim 14, further comprising conducting a perforation operation by ejecting a pressurized fluid through the ports. 